Lead terminal

ABSTRACT

The present invention relates to improved terminals for electrical components having bodies of thermoshrinkable material. More particularly, the present invention relates to a resilient sleeve adapted to be disposed within the body and electrically connected to elements therein and held in position in the body by the shrinking of the body around the sleeve and into holding engagement with the sleeve. The sleeve constituting a socket for receiving and holding a connector or a terminal lead wire.

United States Patent [7 2 Inventor Eugene J. Caires Newtown, Conn. [2]] Appl. No. 831,612 [22] Filed June 9, 1969 [45] Patented May 18, 1971 [73] Assignee Vitramon, Incorporated Monroe, Conn.

(54] LEAD TERMINAL 57.6, 74; 3 17/10l (C), 101 (CC), 261, 242; 29/626, 627, 628; 338/322 [56] References Cited UNITED STATES PATENTS 3,260,907 7/1966 Weller et a]. 317/261 Primary Examiner--Darrel L. Clay Attorney--Arn0ld Grant ABSTRACT: The present invention relates to improved terminals for electrical components having bodies of thermoshrinkable material. More particularly, the present invention relates to a resilient sleeve adapted to be disposed within the body and electrically connected to elements therein and held in position in the body by the shrinking of the body around the sleeve and into holding engagement with the sleeve. The sleeve constituting a socket for receiving and holding a connector or a tenninal lead wire.

PATENTED Mm 8 I97! Fig PRIOR ART I INVENTOR EUGENE J. CAIRES WWW ATTORNEY LEAD TERMINAL BACKGROU ND OF THE INVENTION Heretofore, there have been two methods of inserting a connector or a terminal lead wire into a recess in a component comprising a thermoshrinkable body, such as a ceramic, vitreous, organic or other material requiring a firing or sintering operation before the body is finally fired or hardened. The first method involved coating the interior walls of the recess with a conductive paint, preferably a silver-based composition, and inserting the connector or terminal lead wire directly into the recess. The silver paint functions in a dual capacity as both the connecting medium between conducting elements located in the body, and exposed by the recess, and the terminal lead wire; and, as a resilient buffer to counteract the absence of resilience in the terminal lead wire during the firing to shrink the body intoa gripping relationship around the terminal lead wire. This procedure has the attendant disadvantage that the silver paint must be wet, i.e., retain a moisture content sufficient to maintain flow, while the terminal lead wire is being inserted into the recess so that the paint could'accommodate itself to the substantially rigid lead wires. As a result, in an inordinate number of parts the paint" is displaced or weakened by the insertion of the terminal lead wire. During the firing of the body, this sporadic absence of the buffer" between the rapidly shrinking body and the nonresilient terminal lead wire creates severe pressure differentials. Once the body has hardened, these incorporated pressures are responsible for generation of fissures, which, in turn, can cause failure of the part.

The second method improves upon the above described procedure by inserting a thin resilient sleeve of high-temperature-conducting material into the recess in communication with the exposed electrical elements of the body. As before,

the communication is provided by a layer of silver paint" lin- I ing the walls of the recess. This, however, is accomplished without any of the inherent disadvantages of the first method since the resiliency of the sleeve permits it to conform to any variations in the walls of the recess and, thus, be in intimate contact with the body. In addition, the resiliency of the sleeve provides for a stronger anchorage of the sleeve and a more reliable finished part'because the body can shrink and grip the sleeve tightly during the firing operation without generating pressures or strain as a result of variations in the shrinking rate of the body. After the firing, to secure the sleeve, the terminal lead wire can be inserted and retained by soldering, etc.

Use of the sleeve as areceptacle for the terminal lead wire has many advantages over the direct insertion of the terminal lead wire into the recess. It does, however, have a serious disadvantage. The extremely close tolerance between the sleeve and the terminal lead wire from the clearance fit between the sleeve and the lead wire usually results in the lead wire pushing all, or nearly all, of the solder to the very bottom of the sleeve as the lead wire is inserted into the sleeve. More often than not, a quantity of the silver paint" on the recess wall above the sleeve is also scrapped 011' by the descending lead wire; the paint ending up in the bottom of the sleeve. Since all, or nearly all, of the solder is at the bottom of the sleeve, the connection between the sleeve solder terminal lead wire is indirect relationship to the surface area of the tip end of the lead wire. This area as can be imagined, is extremely small and, as a result, the implacement of the lead wire in the sleeve often does not meet minimum acceptable standards, The presence of silver paint" in the bottom of the sleeve further weakens the connection between the sleeve and the lead wire, first, by contaminating the solder; and, second, since it is contacted and scraped off the walls of the recess above the sleeve by the lead wire, before the lead wire begins pushing the solder to the bottom of the sleeve, the silver is in a layer intermediate the tip end of the lead wire and solder, thereby further reducing the area of direct contact between the solder and lead wire.

SUMMARY OF THE INVENTION The above described disadvantages of a sleeve insert system are overcome while still retaining all the advantages thereofby positioning the sleeve in the recess such that a solder space is created between the floor of the recess and the extreme lower portion of the sleeve sufficient to permit the solder to firmly grasp and retain the terminal lead wire when it is positioned in the sleeve. By this method, the solder blob, forced to the floor of the recess by the piston action of the lead wire as it is inserted through the sleeve, will be in contact with portions of the sidewall of the lead wire as well as the tip end. Thus, the area of contact between the solder and lead wire can be doubled or even tripled without, in any way, altering the dimensions of the recess or the lead wire. For a better and more complete understanding of the present invention, its objects and advantages, reference should be had to the following description taken in conjunction with the accompanying DETAILED DESCRIPTION OF THE INVENTION While the present invention may be used in various electrical components, such as inductors, resistors, transistors, thermistors, and combinations thereof to provide an electrical terminal for an electrical element disposed in a fired body of thermoshrinkable material, it is herein illustrated in connection with capacitors. The capacitor 10 is provided with cooperating partially offset, spaced electrical elements 12, I4 embedded within the dielectric material body 16 in a manner well known in the art. Recesses 18, 20 are formed in the body, for example, by drilling, before firing so as to pass through the offset portions. That is, recess 18 passes through a portion of elements 12 not overlapped by elements 14; and, similarly, recess 20 passes through a portion of elements 14 not overlapped by elements 12. The elements, exposed by the recess are then electrically interconnected, preferably by a coating of a conductive silver paint" (not shown) coated onto the walls of the recess, to form the component into a capacitor.

In accordance with the present invention a resilient sleeve 24, formed of a material capable of withstanding the firing temperature of the body, for example, silver, platinum, palladium, gold or alloys thereof, is inserted into the recesses 18, 20 to form a terminal means for the body. Heretofo're, as shown specifically by FIG. 3, the sleeve was bottomed on' the floor of the recess 18, 20, i.e., inserted until the lowermost extreme 26 of the sleeve 24' physically contacted the floor 28' of the recess 20. With the present invention, however, the lowermost extreme 26 of the sleeve 24 is positioned well above the floor 28 of the recess 18. The reasons for this and the unexpected advantages derived therefrom will become apparent as this description proceeds.

While the sleeve can be provided with slits or the like to make it resilient, it is presently preferred to form the sleeve with a thin resilient wall, such as shown in FIG. 2. A resilient sleeve has the advantage that it can yield when inserted into the lining to prevent excessive scraping of the interconnective coating (not shown) from the walls of the recess and can be securely gripped by the body as it shrinks during the firing.

' The ability of a resilient sleeve to absorb the pressure created by the shrinking body enhances the reliability of the part, first, because it does not return the strain to the body which becomes extremely brittle as an incident to firing; and, second because it enables the sleeve to compensate for variations along the walls of the recess or in shrinking rates of difierent portions of the body.

Once the sleeve is firmly gripped in place the terminal lead wire or other form of connector having a clearance fit relative to the sleeve can be inserted into the sleeve to complete the assembly of the part. This order of manufacture is particularly advantageous since the terminal lead wires do not have to be capable of withstanding the firing temperature of the body, thereby greatly increasing the possible choices of lead wire material.

As described above, the prior art system of sleeve insertion, bottomed the sleeve on the floor of the recess. As a result, all, or nearly all, of the solder positioned in the sleeve in preparation for insertion of the lead wire was forced to the floor of the recess as the clearance fit lead wire traversed through the sleeve during its positioning. Thus, since the solder only contacted the lead wire at its extreme tip end, the interconnection between lead wire and part was often tenuous. In addition, any silver paint" at the bottom of the recess, scraped off by the descending lead wire, further weakened the connection, first, because it contaminated the solder; and, second, because its position, intermediate the solder and lead wire, further reduced the contact area between the solder arid lead wire.

Applicant addressed himself to this problem and he found that he could both retain the sleeve system, with all its attendant advantages, and increase the area of contact between the solder and lead wire to the point where the connection can be assuredto be secure. In addition, he found that this desired tioned in the body the solder blob contacts portions of the sidewall of the lead wire as well as the tip end. In this manner,

the area of contact between the solder and lead wire can be increased by a factor of as much as two or three, thereby correspondingly increasing the strength of the lead wire-body connection.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics of the invention the present embodiments are illustrative and not restrictive. The scope of the invention is defined by the appended claims rather than by the description preceding them, and all embodiments which fall within the meaning and range of equivalency of the claims are, therefore, intended to be embraced by those claims.

Iclaim:

1. In an electronic component comprising a monolithic body of thermoshrinkable material, having embedded therein at least one electrically conductive element; the body having a recess therein extending inwardly from a surface thereof in a direction perpendicular to the major plane of the electrically conductive element and intersecting the electrically conductive element; a resilient sleeve of electrically conductive material positioned in the recess and electrically communicating with the electrically conductive element; and, a lead wire of electrically conductive material insertably positioned with a clearance fit within the sleeve and soldered therein to provide external communication to the electrically conductive element wherein the improvement comprises a space in the recess intermediate the bottom of the recess and the lowermost extreme of the sleeve, the recess providing a reservoir containing solder, a portion of the lead wire extending through and beyond the sleeve and into the recess such that when the lead wire is inserted the portion of the lead wire extending through and out of the sleeve and into the recess is contacted on all sides by the solder in the recess reservoir. 

1. In an electronic component comprising a monolithic body of thermoshrinkable material, having embedded therein at least one electrically conductive element; the body having a recess therein extending inwardly from a surface thereof in a direction perpendicular to the major plane of the electrically conductive element and intersecting the electrically conductive element; a resilient sleeve of electrically conductive material positioned in the recess and electrically communicating with the electrically conductive element; and, a lead wire of electrically conductive material insertably positioned with a clearance fit within the sleeve and soldered therein to provide external communication to the electrically conductive element wherein the improvement comprises a space in the recess intermediate the bottom of the recess and the lowermost extreme of the sleeve, the recess providing a reservoir containing solder, a portion of the lead wire extending through and beyond the sleeve and into the recess such that when the lead wire is inserted the portion of the lead wire extending through and out of the sleeve and into the recess is contacted on all sides by the solder in the recess reservoir. 